Packing materials in the shape of tubular elements, which are sealed in the longitudinal direction by means of bonding and are capable of being shaped into bags for the above-mentioned use, have already been proposed. According to a known embodiment, the wall of the tubular element consists of at least two overlapping elements which are made of different materials, specifically an outer layer or film made of a material that is impermeable to gases and an inner layer or film made of a thermoplastic, heat-sealable material. The two layers are intimately overlapped, and at least the inner layer has an embossing or a network of channels, which promote the outlet of air at the time the bag is used for vacuum-packing. Therefore, the network of channels is obtained on the inner, heat-sealable layer of the element.